Circuit for matching the load impedance of an electronic device

Abstract

A circuit matches the load impedance of an electronic device. The circuit comprises an impedance network, a control circuit suitable for varying the impedance of said network and a sensor coupled with said network and said load and suitable for detecting the ratio between the incident and reflected standing waves in transferring power from the electronic device to the load; the sensor is suitable for providing two signals substantially proportional to the incident and reflected amplitude of the waves at the control circuit. The impedance network is a network of variable resistances and the control circuit is suitable for varying the value of the resistances to lower said ratio between the incident and reflected standing waves to a value that ensures the transfer of power from the electronic device to the load.

Description

BACKGROUND[0001]1. Technical Field[0002]The present invention relates to a circuit for matching the load impedance of an electronic device.[0003]2. Description of the Related Art[0004]Electronic circuits operate on a load that is suitably matched to display their nominal performance. This becomes particularly important for radio-frequency circuits, especially for power amplifiers of radio transmitters.[0005]Using impedance matchers is known in the prior art. A solution near to the needs of high-integration radio-frequency systems is known from U.S. Pat. No. 379,494. Said patent discloses an antenna tuner of automatic type that comprises digital control circuits for selecting reactive tuning elements of an antenna impedance coupling network. The tuner system provides rapid transformations of impedance of a multiple antenna to the load resistance to effectively transfer the power of a power amplifier of a portable radio transmitter to each antenna selected above a wide frequency range...

AI Technical Summary

Benefits of technology

[0013]One embodiment is a circuit for matching the load impedance of an electronic device, said circuit comprising an impedance network, a control circuit suitable for varying the impedance of said network and a sensor coupled with said network and said load and suitable for detecting the ratio between the incident and reflected standing waves in transferring power from the electronic device to the load, said sensor being suitable for providing two signals substantially proportional to the amplitude of the incident and reflected standing waves on said control circuit, wherein said impedance network is a network of variable resistances and said control circuit is suitable for varying the value of the resistances to lower said ratio between the incident and reflected standing waves to a value that ensures the transfer of power from the electronic device to the load.

Problems solved by technology

Nevertheless, they are affected by different types of problem such as the dimension of the corrector and the cost thereof, frequency sensibility, the complexity of load impedance detection and of control strategy.

The first problem is due to the need to create numerous modulated high impedance inductances, to working frequencies and to the need to conduct great quantities of current if the application is power amplification.

The second problem depends on the correction strategy, which is based on using reactive elements the impedance of which depends on the frequency; wishing to use the corrector for multiband applications will thus require making distinct blocks, to be used according to the application.

The use of LC networks in systems with very broad bands, on the other hand, is impossible.

The third problem depends on the need to know the module and phase of the load impedance exactly, which thus makes complex circuits for monitoring impedance and sophisticated control strategies necessary.

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